JPH09157726A - Method for detecting and predicting slopping - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for accurately detecting and predicting the development of slopping by extracting a vibration signal sufficiently corresponding to the furnace condition. SOLUTION: In a refining furnace for blowing oxygen into the furnace, a sensor for measuring the vibration is fitted to a lance and the vibration developed in the lance at the time of blowing into the refining furnace or at the time of pretreating, is measured. In this measured value, the vibration generated at the time of changing the flow rate of gaseous oxygen or at the time of charging auxiliary raw material is removed through a band pass filter. Only the frequency component sufficiently corresponding to the furnace condition is extracted and the slopping is accurately detected and prodicted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting and predicting sloping that occurs during blowing or pretreatment in a refining furnace such as a converter or a pretreatment furnace in which oxygen is blown into the furnace.

[0002]

2. Description of the Related Art In a refining furnace such as a converter or a pretreatment furnace, for example, when blowing the converter, an oxygen jet is blown through the lance onto the surface of the steel bath to stir and react the slag. To remove impurities in the steel bath. In this blowing, the phenomenon of so-called sloping, in which slag and molten steel are scattered from the furnace opening, occurs when the slag becomes more slagified and the decarburization rate increases.

This sloping causes a decrease in yield due to the outflow of molten steel, a work environment is deteriorated by smoke and quiche generated at this time, and an operating loss occurs. Therefore, it is necessary to detect and predict sloping during operation. is important.
As a method for detecting and predicting this slopping, a vibration measuring method, an exhaust gas analyzing method, a furnace sound measuring method, a microwave irradiation method, a furnace pressure measuring method and the like have been conventionally known.

Among the methods for detecting and predicting the above-mentioned slopping, the conventional vibration measuring method is to install a large number of vibrometers on a lance or a furnace body, and to measure the previous measured value and the measured value of each of the vibrometers. Sloping was detected by calculating the difference and calculating the average value of them. However, this method has a drawback that the system is complicated because it requires calculation and analysis of many measured values.

Therefore, in order to eliminate the above drawbacks, some improved vibration measuring methods have been proposed in the past. For example, in Japanese Patent Laid-Open No. 4-301028, the frequency of the lance at the time of blowing is measured by a sensor provided on the lance, the measured value is passed through a low-pass filter to extract only low-frequency components, and A method for detecting sloping by removing vibrations when changing the flow rate of oxygen gas or introducing auxiliary materials is described.

Further, in Japanese Laid-Open Patent Publication No. 55-76008, an accelerometer is provided on the lance, and the acceleration change in the low frequency region based on the natural frequency of the lance and the hose is erased from the measured value to increase the frequency. A method for separating oscillating parts and detecting sloping is described.

However, in the former method in which the measured vibration value is passed through a low-pass filter to extract the low-frequency component, the vibration and the length of the lance at the time of feeding the auxiliary raw material to a frequency range lower than the vibration component corresponding to sloping. However, vibration due to weight change and vibration in the low frequency range due to natural vibration of the lance and the hose are included, and it is difficult to extract only the vibration component corresponding to sloping.

In the latter method, in which the vibration portion in the low frequency range due to the natural vibration of the lance and the hose is separated to extract the vibration in the high frequency range, the influence of the natural vibration of the lance and the hose and the change of the lance height are changed. Although it is possible to exclude the influence of the change in the length from the fulcrum to the tip of the lance and the change in the weight of the lance due to the adhesion of metal to the lance, it is affected by the high frequency chatter vibration of the lance itself due to the high-speed blowing of oxygen. In addition, there is a problem that the vibration changes when the amount of acid fed is changed.

[0009]

As described above, the conventional improved vibration measuring method has various problems, and it is difficult to accurately extract only vibrations that correspond well to the furnace conditions. there were. Further, the sensor and the cable part attached to the lance are exposed to the high temperature in the furnace, and are easily damaged, and lack in durability.

In view of the above situation, the present invention extracts a vibration signal that corresponds well to the state of slagging in the furnace, that is, the state of the furnace, by a simple processing method, and accurately detects and predicts the occurrence of sloping. (EN) A sloping detection / prediction method capable of protecting a sensor by avoiding a heat load from the furnace side without modifying an existing lance.

[0011]

Means for Solving the Problems The present inventor has conducted various studies to achieve the above-mentioned object, analyzing lance vibration during blowing in a refining furnace, and passing a vibration measurement value through a bandpass filter, Only vibrations that correspond well to the slagging state during blowing, i.e., the furnace conditions, are extracted, and vibration changes when low-frequency auxiliary raw materials are input, length changes from the lance fulcrum due to lance height changes, and metal adhesion It was learned that vibration changes due to the natural vibrations of the lance and the hose due to weight changes, or high frequency chatter vibrations when changing the amount of oxygen supply can be eliminated. The present invention has been completed as follows based on the above findings.

In a refining furnace in which oxygen is blown into the furnace, a vibration measuring sensor is attached to the lance, the vibration generated in the lance during blowing or pretreatment of the refining furnace is measured, and the measured value is passed through a bandpass filter. A sloping detection / prediction method characterized by eliminating vibrations that occur when the flow rate of oxygen gas is changed or when introducing auxiliary materials, and extracting only the frequency components that correspond well to the furnace conditions to accurately detect / predict.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The lance in a refining furnace in which oxygen is blown into the furnace vibrates due to blowing and constantly vibrates during blowing. This vibration is caused by foaming, which is a state in which slag is foaming due to the progress of slag formation, when motion is received from the slag during further progressing slag, when the amount of oxygen supply is changed, or when auxiliary materials are added. In addition, a vibration waveform that combines vibrations that change at frequencies near the natural frequency of the lance and hose due to changes in the length from the fulcrum due to changes in the lance height and changes in weight due to the attachment of metal to the lance can be obtained. .

Therefore, sloping can be detected accurately.
In order to predict, it is necessary to extract only the lance vibration due to the movement of the slag during forming or sloping and remove the vibration change due to other factors to prevent erroneous detection.

For example, in a 250-t converter, frequency analysis of the vibration change of the lance during blowing is such that the vibration in the low frequency range of about 10 Hz or less is based on the natural frequency of the lance and the hose, The vibration change of the lance and hose when it collides with the lance at the time of throwing in, the length change from the fulcrum due to the change of the lance height, and the vibration change due to the weight change due to the adhesion of metal to the lance are in this frequency range. It does not directly indicate the lance vibration due to the slag generated by the change in the furnace conditions. Further, the chatter vibration of the lance when changing the amount of oxygen to be sent occurs in a high frequency range of about 100 Hz or higher, and the vibration in this frequency range does not directly indicate the lance vibration due to the slag generated by the change in the furnace condition.

When the vibrations in the normal blowing state and the foaming or slagging state in which the slag is foamed due to the progress of slag formation are compared in the frequency range, as shown in FIG. 1, it depends on the slag during forming or sloping. The vibration change of the lance appears mainly in the frequency range of 10 to 80 Hz.

It is expected that this frequency range will have different values depending on the profile of the furnace, but by using a bandpass filter that passes such a frequency range,
Minimize the effects of vibration changes due to changes in operating conditions other than lance vibrations (changes in the amount of oxygen supply, input of auxiliary materials, length changes from the fulcrum due to changes in lance height, etc.), and only lance vibrations due to slags It becomes possible to extract,
By using the extracted vibration, it is possible to easily and more accurately detect and predict sloping.

Regarding the vibration measuring sensor, it is desirable to attach a heat shield plate to a portion of the lance that is inserted into the furnace through the upper hood and that is exposed above the upper hood, and install it on the upper side to avoid thermal influence. .

[0019]

An embodiment of the present invention will be described with reference to the drawings.
2 (A) and 2 (B) are explanatory views showing the outline of a converter in which a vibration measuring sensor for carrying out the present invention is attached to a lance. A heat shield plate 5 is provided on a portion of the lance 2 inserted into the furnace through the upper hood 7 of the converter 1 so as to project above the upper hood 7, and an accelerometer 3 serving as a vibration measuring sensor is provided above the heat shield plate 5. Is attached to the lance 2 with the fixture 4. The fixture 4 is composed of a belt wound around the lance 2 and is detachably provided by a fixing member 6 such as a patch lock. In this example, the accelerometer is used as the vibration measuring sensor, but if the existing equipment can be easily installed, another load vibration measuring sensor such as a load cell may be used.

As shown in FIG. 3, the device for detecting and predicting sloping passes the measurement signal detected by the accelerometer 3 through the amplifier 8 and the band pass filter 9,
Take out only the vibrations that correspond well to the furnace conditions due to slag,
Further, the wave is detected through the full-wave rectifier 10 and input to the arithmetic unit 11. Here, the sloping prediction determination is performed based on the vibration amplitude amount P and the amplitude change amount Q, the determination result is displayed on the furnace condition determination display 12, and the sloping prediction warning device 13 is configured to give an alarm. . Based on the result of the determination of the furnace condition, measures such as the introduction of the suppressor and the change of the amount of oxygen transfer are performed.

With the above apparatus, only the vibrations corresponding to the furnace condition due to the slag are taken out and detected, and the vibration amplitude amount and the amplitude change amount are as shown in FIGS. 4 (A) and 4 (B). It corresponds well to whether or not sloping will occur thereafter. However, the amplitude change amount = current lance vibration amplitude amount−lance vibration amplitude amount 5 seconds before.

From the results shown in FIGS. 4 (A) and 4 (B), the vibration amplitude amount P is calculated as shown in Table 1 by using the vibration amplitude amounts C ₁ , C ₂ and C ₃ shown in FIG. 4 (A). The current furnace condition can be determined by dividing the level into stages, and the occurrence of sloping and its degree can be determined by dividing the amplitude change amount Q by D _{1 to} D ₄ as shown in FIG. 4 (B). I can predict.

[0023]

[Table 1]

In this way, when the occurrence of sloping is predicted, the arithmetic unit controls the sloping by changing the setting of the amount of acid to be fed and the amount of the sloping suppressor to be charged according to the expected degree of sloping. Be seen. As a result, the occurrence of sloping is prevented, the occurrence rate of sloping is greatly reduced, and it can contribute to the stable operation of the refining furnace.

[0025]

According to the present invention, only the vibration of the lance due to the movement of the slag can be extracted, and the occurrence and the degree of sloping can be predicted more simply and more accurately.

[Brief description of the drawings]

FIG. 1 is a graph showing a comparison between vibration in a normal blowing state and vibration in a forming or sloping state in a frequency range.

FIG. 2 is an explanatory view showing the attachment of the vibration measuring sensor to the lance in the embodiment of the present invention, (A) is a front view,
(B) is a plan view.

FIG. 3 is a block diagram showing an example of an apparatus for implementing the present invention.

FIG. 4 is a graph showing correspondences between lance vibration measurement values and furnace conditions and presence / absence of sloping, (A) relationship between vibration amplitude amount and furnace condition determination, (B) vibration amplitude amount and vibration amplitude change amount. Relationship with.

[Explanation of symbols]

 1 Converter 2 Lance 3 Accelerometer 4 Fixture 5 Heat shield 6 Fixing bracket 7 Upper hood 8 Amplifier 9 Bandpass filter 10 Full wave rectifier 11 Arithmetic unit 12 Reactor status indicator 13 Sloping predictive alarm

Claims (1)

[Claims] 1. A refining furnace in which oxygen is blown into the furnace,
A vibration measuring sensor is attached to the lance to measure the vibration generated in the lance during blowing or pretreatment of the refining furnace, and the measured value is passed through a bandpass filter to change the flow rate of oxygen gas or when the auxiliary material is charged. The sloping detection / prediction method is characterized in that only the frequency components that correspond to the furnace conditions are removed and the detection / prediction is accurately performed.